This device relates generally to the field of smoke detectors and more particularly to a smoke detector having an audible indicator for warning of the absence of the primary power source powering the smoke detector, whether that primary power source is a battery, an AC power source, or an AC power source with battery back-up.
It has been determined that many fire related fatalities may have been avoided if the victims had been provided with adequate warning of a fire provided by an operating smoke detector. Many times, a smoke detector is present but a missing battery or the disconnection of the AC power to a smoke detector results in a lack of power necessary to operate the smoke detector. This results in a lack of adequate warning of the presence of smoke and fire. As such, it has been recognized in the art of smoke detectors that it is useful to provide a smoke detector having a visible indicator to warn the consumer that a smoke detectors primary power source has been disconnected. U.S. Pat. Nos. 4,228,428, 4,881,063, 4,959,640, 5,055,830, and 5,103,216 relate to smoke detectors that provide a visual indicator if a battery is not installed in the smoke detector. U.S. Pat. No. 4,870,395 shows a smoke detector having a safety lockout system that prevents securing the body of the smoke alarm to the mounting bracket prior to the installation of a battery.
Additionally, U.S. Pat. No. 3,594,751 describes a smoke detector having a primary battery and a standby or replacement battery, and circuit means causing the standby battery to continually monitor the strength of the primary battery and to give a supervisory warning to the homeowner when the strength of the primary battery falls below a predetermined value, whereby the homeowner is warned to replace the primary battery with the standby battery and to secure in a reasonable time a fresh replacement for the standby battery. A new battery should be installed as promptly as reasonably possible into the supervisory position or supervision will be lost. In any event, according to the patent, the supervisory circuit (assuming a charged battery is in position in the supervisory circuit) will always inform the homeowner or proprietor of the fact that the primary battery is due to be replaced.
U.S. Pat. No. 4,761,631 discloses a vehicular burglar alarm system with a backup battery which supplies power to a vehicle alarm system. The main battery charges and maintains a backup battery in full charge, and when the main battery is disconnected or damaged, the backup battery provides power to an alarm and a control circuit triggers a siren to give warning.
U.S. Pat. No. 4,929,931 discloses a battery monitor for monitoring a plurality of conditions of a battery utilized within a system as the primary or auxiliary power source of the system. A processor utilizes a voltage measurement to determine the presence or the absence of the battery, whether the battery voltage is equal to or greater than a nominal voltage level, and whether the discharge rate of the battery is greater than a selected discharge rate.
None of the above systems, however, takes into consideration the possibility that the user of the smoke detector may have intentionally disabled the power source to the detector, rendering it inoperable, and may thereafter lack the proper motivation to replace or reconnect power to the detector. For example, it is not uncommon for a consumer to purposely remove a battery from a battery powered smoke detector, or an AC detector having a battery backup, to use the battery in another household appliance. Further, that same consumer may lack the motivation to replace the borrowed battery. When a fire occurs, (and in the case of AC units having a battery backup, when the AC power supplying the detector goes out), the consumer's battery operated appliance may work, but their smoke detector will not.
A second common problem with battery powered detectors involves the low battery warning signal built into battery powered and battery backup smoke detector circuits. When a smoke detector battery becomes low, the horn will periodically emit an annoying `chirp` sound. Many people will disconnect or remove the battery so as to discontinue the `chirp` warning and will, again, lack sufficient motivation to replace the battery, thus leaving the detector unpowered.
Further, if a smoke detector is improperly located too close to sources of combustion, in a kitchen for example, a person may remove the battery or disconnect the AC power source to the unit to prevent annoyance caused by nuisance activations.
Additionally, conventional AC powered smoke detectors have no easily discernible way of alerting the user that the AC power has been removed or disconnected from the detector. In many cases, all of the AC powered smoke detectors in a home may be part of the same electrical circuit and may all be be connected to the same circuit breaker. If that circuit breaker were to open due to a short or other abnormality in the circuit, or if a power outage were to occur, a consumer may never be alerted to the fact that some or all of the AC powered smoke detectors have been disabled. Normally, consumers will presume that an AC detector is powered and fail to test such a unit.
None of the prior art smoke detector systems provides the consumer with an audible warning that the primary power source to the detector has been disconnected and also provides the consumer with sufficient motivation to promptly reconnect the primary power source to a disabled smoke detector.
It is therefore desirable to provide an audible warning system that alerts the consumer that the primary power source to an AC-powered, AC-powered with battery backup, or battery-powered smoke detector has been disabled. It is additionally desirable to provide a smoke detector having a means to provide a consumer (or anyone else within hearing range) with sufficient motivation to replace or reconnect the power source to a disabled smoke detector so that it will be operable in the event of a fire.